Various control systems now utilized in passenger cars require input information related to vehicle velocity and/or wheel angular velocity. Controlled braking systems generally require a signal related to wheel angular velocity to avoid wheel lockup and consequent skidding. This signal has been provided by utilizing a "tone wheel", a slotted disc driven as a function of wheel rotation, and an inductive sensor positioned adjacent the tone wheel to provide frequency-indicating output signals which vary in frequency as a function of the vehicle wheel angular velocity. Of course other types of sensors, such as a light-emitting unit which has its radiation alternately blocked and passed by apertures in a driven disc, and a radiation-sensitive sensor or pickup unit, can also be used in a place of a tone wheel and inductive sensor. Some control circuits were developed for use with a tone wheel having 120 teeth, thus providing 120 cycles of the output signal for each complete revolution of the tone wheel. Some automotive manufacturers desired to utilize tone wheels with only 60 teeth, which necessitated major redesign of the band pass and other circuits in the existing control systems. This would entail considerable expense and time, and it is clearly desirable to obviate such expense and time, if possible.
It is therefore a primary consideration of this invention to provide an automotive vehicle control circuit suitable for use with tone wheels having 60 teeth and providing output information at a rate corresponding to that of systems employing 120 tooth tone wheels.